A semiconductor device is known to be manufactured through a step of forming a photoresist pattern on a base material by lithography. Recently, to satisfy the requirement for further reducing the dimensions of a semiconductor device, immersion lithography has been proposed. In this technology, during a light exposure step, a liquid immersion medium of a predetermined thickness is placed on an optical path between the film to be exposed to light formed on a substrate and a light-exposure device (lens), at least on the film, and light is applied to the film to form a resist pattern. In this manner, the space of the optical path of exposure light is filled with a liquid immersion medium having a refractive index (n), which is greater than that of the air or inert gas and smaller than that of a resist film, in place of the air or inert gas such as nitrogen used in a conventional method. By virtue of this, high resolution can be obtained similarly to the case where a shorter-wavelength light is used or the case where a high NA lens is used, even if the wavelength of the light source for exposure be unchanged. In addition, there is another advantage in that focal depth latitude is not decreased. Accordingly, if immersion lithography mentioned above is used, a resist pattern increased in resolution and improved in depth of focus can be formed by using the lens attached to a light exposure apparatus so far employed and by incurring no extra development cost for especially manufacturing a high-resolution lens for micro-fabrication. Because of this, immersion lithography has attracted great attention.
In addition, in either one of conventional lithography and immersion lithography, a resist pattern is formed by using a resist film selected so as to correspond to the wavelength of exposure light such as g-line light, i-line light, KrF excimer laser, ArF excimer laser or EUV; an anti-reflective film provided as a lower layer of the resist film; and a protective film formed as an upper layer of the resist film. However, when these films are formed, a photosensitive resist-film forming coating solution adheres to a back surface portion of a substrate and an edge portion thereof, staining the substrate. The solution unnecessarily adhered to the portions must be cleaned and removed prior to performing the next process step.
In lithography, when the photosensitive resist film thus formed is exposed to light for pattern formation and developed to form a resist pattern, it is necessary to clean and remove resist remaining uncured. Furthermore, since the resist pattern thus formed is no longer needed after a semiconductor device is manufactured by etching, the whole resist present on the substrate must be cleaned and removed.
As is described above, in lithography, a cleaning operation must be performed several times for removing a resist coating film.
In lithography, besides these cleaning operations, a cleaning operation is performed for cleaning the surface of a substrate before a coating film is formed thereon. Furthermore, a cleaning operation is performed for removing stain adhered to a machine for supplying a base material with materials for forming various types of coating films, such as a resist film, an anti-reflective film and a protective film, optionally for preventing stain from affecting a series of steps for forming a resist pattern.
To carry out various types of cleaning operations, cleaning solutions suitable for individual purposes are required. However, the number of supply pipes for cleaning solutions for lithography to be provided to a semiconductor manufacturing line is limited. For the reason, a universal cleaning solution, which is applicable, as commonly as possible, to materials for forming various types of coating films and objects to be removed for different purposes, is required.
Additionally, the cleaning solution for lithography must satisfy basic cleaning properties such as ability to dissolve and remove an unnecessary part effectively in a short time, ability to get dry quickly in a short time, and ability not to affect the shape of the resist film purposely left for use in the step to follow. In addition, the cleaning solution must satisfy requirement to produce no harmful effect on the environment and human body, ensure safety and be available at low cost.
To satisfy these requirements, the following cleaning solutions for lithography have been proposed. Examples thereof include cleaning solutions for lithography consisting of a single component, such as a cleaning solution consisting of a solvent based on ethyleneglycol or an ester thereof (JP5-75110B), a cleaning solution consisting of propyleneglycol alkyl ether acetate (JP4-49938B), a cleaning solution consisting of alkyl 3-alkoxypropionate (JP4-42523A) and a cleaning solution consisting of alkyl pyruvate (JP4-130715A); and cleaning solutions for lithography using a mixture of two kinds or more of solvents, such as a cleaning solution using a mixture of propyleneglycol alkyl ether, monoketone having 1 to 7 carbon atoms and lactam or lactone (JP11-218933A), a cleaning solution for lithography containing n-types of solvents satisfying 9≦Σxiδi≦12, wherein xi is defined as a weight proportion of a component i and δi is defined as a solubility parameter calculated with a Fedors method (JP2003-114538A), and a cleaning solution using a mixture of acetic ester, γ-butyrolactone and a non-acetic ester (JP2003-195529A).
However, some of these cleaning solutions for lithography are lack of basic cleaning capability or dryability. Others which satisfy these requirements, only have a good cleaning effect on a specific coating film and no sufficient cleaning effect on other coating films. Still others have drawbacks in that the yield of a product decreases and that the effect of removing unnecessary resist varies depending on the portion where it adhered. In short, these cleaning solutions do not satisfy either one of basic properties and requisite properties as a cleaning solution for lithography and are not always satisfactory in view of practical use.